A Space Vector Modulation Strategy for PMSMs Operating at Low Switching-to-Fundamental Frequency Ratio

A novel space vector modulation (SVM) strategy for a permanent magnet synchronous machine drive, operating at low switching-to-fundamental frequency ratio, is presented in this article. The proposed strategy is based on applying more than two active vectors in a switching period, aiming to consider the expected rotation and possible movement from one sector to another of the voltage reference vector within that period. The method is simple as the calculation of the duty cycles is still based on the expressions for a conventional SVM. Current distortion and efficiency calculations are also provided, comparing the proposed SVM with conventional SVM and six-step modulation. The results show that the proposed method generates a current distortion similar to the conventional SVM at high frequency ratios but much lower at low frequency ratios. Moreover, comparing with six-step modulation, the current distortion generated by the proposed SVM is always lower, independent of the frequency ratio. On the other hand, the efficiency of the inverter obtained with the proposed SVM is higher than the one obtained with conventional SVM. The effectiveness of the proposed strategy is validated via simulations and experiments.